Tire

ABSTRACT

A tire ( 1 ) is provided with multiple projection parts ( 500 ) in a groove bottom ( 50 B 2 ) of a groove portion. The projection parts ( 500 ) extend from one side wall ( 50 B 1 ) to the other side wall ( 50 B 3 ) opposed to the one side wall ( 50 B 1 ), the side walls forming the groove portion. The projection parts ( 500 ) are arranged at predetermined intervals in the groove portion. A relationship of 0.75 L≦P≦10 L is satisfied where L denotes a length of the projection parts ( 500 ) and P denotes the predetermined intervals. In addition a relationship of 0.4≦FW/W&lt;1 is satisfied, where W denotes a groove width of the groove portion and FW denotes a length of the projection parts ( 500 ) in an orthogonal direction which is orthogonal to the extending direction of the groove portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2013/068342 filed Jul. 4, 2013, claiming priority based onJapanese Patent Application No. 2012-150915 filed Jul. 4, 2012, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a tire designed to suppress atemperature rise during driving.

BACKGROUND ART

Heretofore, pneumatic tires (hereinafter referred to as tires) put onvehicles have been using various methods for suppressing a temperaturerise in the tires during driving of the vehicles. Heavy-loading tiresput on trucks, buses, and construction vehicles, in particular, aresubjected to a remarkable temperature rise.

To address this, there has been known a tire provided with many fin-likeprojections on its side wall of the tire (see Patent literature 1, forexample). With such a tire, the fin-like projections generate aturbulent flow in an air flow passing along the surface of the side wallsection when the tire is rotated on a road, and the turbulent flowsencourage heat dissipation from the tire. Thus, a temperature rise inthe side wall section is suppressed.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Publication No.2009-160994 (pp. 4 and 5, FIG. 2)

SUMMARY OF INVENTION

The aforementioned conventional tire, however, has the following pointto be improved. Specifically, use of the projections on the side wallsection alone has a limitation on efficient suppression of a temperaturerise in the tread section.

The present invention has been made in consideration of suchcircumstances, and has an object to provide a tire capable ofeffectively suppressing a temperature rise of a tread section duringdriving of a vehicle.

To attain the above-mentioned object, the present invention hasfollowing features. A tire according to the present invention is a tire(tire 1) including a tread section (tread section 5) with a grooveportion (circumferential groove 50B) extending in a tire circumferentialdirection (tire circumferential direction tcd), wherein multipleprojection parts (projection parts 500) are formed on a groove bottom(groove bottom 50B2) of the groove portion, the projection parts eachextend from one side wall (side wall 50B1) to the other side wall (sidewall 50B3) opposed to the one side wall, the side walls forming thegroove portion, the projection parts are arranged at predeterminedintervals in the groove portion, a relationship of 0.75 L≦P≦10 L issatisfied in a tread face view, where L denotes a length of theprojection parts along a groove center line (groove center line WL)passing the widthwise center of the groove, and P denotes thepredetermined intervals. In addition a relationship of 0.4≦FW/W<1 issatisfied, where W denotes a groove width of the groove portion and FWdenotes a length of the projection parts in an orthogonal directionwhich is orthogonal to the extending direction of the groove portion.

The present invention can provide a tire capable of effectivelysuppressing a temperature rise of the tread section during driving avehicle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded view illustrating a tread pattern of a tire 1according to this embodiment.

FIG. 2 is a sectional view illustrating the tire 1 according to thisembodiment along a tire radial direction trd and a tread width directiontwd.

FIG. 3 is an enlarged perspective view illustrating a land block 100.

FIG. 4 is a plan view illustrating a circumferential land portion 70A ina tread face view.

FIG. 5(a) to FIG. 5(c) are enlarged plan views illustrating a recessportion 300 in the tread face view.

FIG. 6 is a partial cutaway perspective view illustrating acircumferential groove 50B.

FIG. 7 is a view illustrating the shape of the circumferential groove50B in the tread face view (when viewed from above the tread section 5).

FIG. 8 is a view illustrating the shape of the circumferential groove50B when viewed from a direction of F5 in FIG. 7.

FIG. 9 is a sectional view illustrating the circumferential groove 50B(projection part 500) taken along a line F6-F6 in FIG. 7.

FIG. 10 is a view illustrating a shape of a circumferential groove 50Bin a tread face view according to the modification example.

FIG. 11 is a view illustrating a shape of the circumferential groove 50Bviewed from an F7 direction in FIG. 10.

FIG. 12(a) is a view illustrating the circumferential groove 50Baccording to this embodiment in the tread face view, and FIG. 12(b) is aview illustrating the shape of the circumferential groove 50B whenviewed from the direction of F5 in FIG. 7.

FIG. 13 is a chart illustrating relationship between an angle θf andthermal conductivity of the circumferential groove (represented inindex).

FIG. 14 is a chart illustrating relationship between a coefficient as amultiplier of a length L of the projection parts and the thermalconductivity of the circumferential groove.

FIG. 15 is a chart illustrating relationship between a coefficient as amultiplier of a groove depth D of the projection parts and the thermalconductivity of the circumferential groove.

FIG. 16 is a plan view illustrating a circumferential land portion 70Ain accordance with another embodiment in the tread face view.

FIG. 17 is a plan view illustrating a circumferential land portion 70Ain accordance with another embodiment in the tread face view.

FIG. 18 is an enlarged perspective view illustrating a tread section 5in accordance with another embodiment.

FIG. 19 is a plan view illustrating a circumferential land portion 70Ain accordance with another embodiment in the tread face view.

FIG. 20 is an enlarged perspective view illustrating a tread section 5in accordance with another embodiment.

FIG. 21 a plan view illustrating a circumferential land portion 70A inaccordance with another embodiment in the tread face view.

FIG. 22(a) to FIG. 22(g) are views illustrating modification examples ofthe sectional shape of a projection part 500.

DESCRIPTION OF EMBODIMENTS

An example of a tire according to the present invention will bedescribed with reference to figures. The following describes (1) astructure outline of a tire 1, (2) a structure outline of an air supplymechanism, (3) a structure outline of a recess portion 300, (4) astructure outline of projection parts 500, (5) actions and effects, (6)comparative evaluation, and (7) other embodiments.

In the following description of the drawings, the same or similarreference signs denote the same or similar elements and portions. Inaddition, it should be noted that the drawings are schematic and ratiosof dimensions and the like are different from actual ones. Therefore,specific dimensions and the like should be determined in considerationof the following description. Moreover, the drawings also includeportions having different dimensional relationships and ratios from eachother.

(1) Structure Outline of Tire 1

The structure outline of the tire 1 according to this embodiment will bedescribed with reference to FIGS. 1 and 2. FIG. 1 is an exploded viewillustrating a tread pattern of the tire 1 according to this embodiment.FIG. 2 is a sectional view illustrating the tire 1 according to thisembodiment taken along a tire radial direction trd and a tread widthdirection twd.

The tire 1 is assembled to a rim that is a normal rim. The tire 1 has anormal internal pressure, and is subjected to a normal load. The rim isprovided with a rim flange. The rim flange supports bead sections 3 inthe tread width direction twd.

For convenience of description, it is assumed that the tire 1 is put ona vehicle, and rolls in a rotation direction tr1 when the vehicle movesforward. The rotation direction of the tire 1 in a state put on thevehicle is not specifically limited.

The “normal rim” refers to a standard rim in an applicable size recitedin Year Book 2008 published by JATMA (The Japan Automobile TyreManufacturers Association, Inc.). In countries other than Japan, the“normal rim” refers to standard rims in applicable sizes recited in thefollowing standards.

The “normal internal pressure” refers to a pneumatic pressure defined bya tire measuring method (pp. 0-3, section 5) recited in Year Book 2008published by JATMA (The Japan Automobile Tyre Manufacturers Association,Inc.). In countries other than Japan, the “normal internal pressure”refers to pneumatic pressures at measurement of the tire size, which arerecited in the following standards.

The “normal load” refers to a load corresponding to a largest loadcapability in a single wheel recited in Year Book 2008 published byJATMA (The Japan Automobile Tyre Manufacturers Association, Inc.). Incountries other than Japan, the “normal load” refers to largest loads(largest load capabilities) in single wheels in applicable sizes recitedin the following standards.

The standards are determined by industrial standards effective in localareas where tires are manufactured or used. For example, the standard inUnited States is

“Year Book of The Tire and Rim Association Inc.,” and the standard inEurope is “Standards Manual of The European Tire and Rim TechnicalOrganization”.

As shown in FIGS. 1 and 2, the tire 1 includes the bead sections 3, atread section 5, a side wall section 7, and a buttress section 9.

The bead section 3 has bead cores 10. The bead sections 3 are in contactwith the rim.

The tread section 5 has a tread face 5 a to come into contact with aroad surface. The tread section 5 has a tread end 5 e that is an outerend of the tread section 5 in the tread width direction twd. The treadpattern of the tread section 5 has a shape symmetric with respect to apoint on a tire center line CL.

The side wall section 7 forms a side face of the tire 1. The side wallsection 7 is located between the bead section 3 and the buttress section9. The side wall section 7 connects the bead section 3 to the treadsection 5 via the buttress section 9.

The buttress section 9 extends inward in the tire radial direction trdfrom the tread end 5 e that is an outer end of the tread section 5 inthe tread width direction twd. The buttress section 9 extends continuousto the side wall section 7. The buttress section 9 is located betweenthe tread section 5 and the side wall section 7.

The inner position of the buttress section 9 in the tire radialdirection trd corresponds to the innermost position of an opening areaof the tread end 5 e in below-mentioned lateral groove portion (luggrooves 60) in the tire radial direction trd. The buttress section 9 isout of contact with a road during normal driving.

As shown in FIG. 2, the tire 1 is a pneumatic tire. The tire 1 has alarger rubber gauge (rubber thickness) at the tread section 5 thanpneumatic tires put on passenger cars and the like.

Specifically, the tire 1 satisfies a relationship of DC/OD≧0.015, whereOD denotes the tire outer diameter, and DC denotes the rubber gauge ofthe tread section 5 at a position on the tire center line CL.

The tire outer diameter OD (unit: mm) is the largest outer diameter ofthe tire 1 (generally, at the tread section 5 near the tire center lineCL). The rubber gauge DC (unit: mm) is the rubber thickness of the treadsection 5 on the tire center line CL. The rubber gauge DC does notinclude the thickness of belt layers 30. As shown in FIG. 2, in the casewhere a circumferential groove 50C is formed in an area including thetire center line CL, the rubber gauge is the rubber thickness of thetread section 5 adjacent to the circumferential groove 50C.

As shown in FIG. 2, the tire 1 includes the pair of bead cores 10, acarcass layer 20, and the multiple belt layers 30.

The bead cores 10 are provided in the bead sections 3. The bead cores 10each are formed of a bead wire (not shown).

The carcass layer 20 forms a frame for the tire 1. The carcass layer 20spans the tread section 5 to the bead sections 3 through the buttresssections 9 and the side wall sections 7.

The carcass layer 20 straddles a space between the pair of bead cores10, and is troidal-shaped. In this embodiment, the carcass layer 20warps the bead cores 10. The carcass layer 20 is in contact with thebead cores 10. Both ends of the carcass layer 20 in the tread widthdirection twd are supported by the pair of bead sections 3.

The carcass layer 20 has a carcass cord extending in a predetermineddirection in a tread face view. In this embodiment, the carcass cordextends in the tread width direction twd. An example of the carcass cordis a steel wire.

The belt layers 30 are disposed on the tread section 5. The belt layers30 are located outside the carcass layer 20 in the tire radial directiontrd. The belt layers 30 extend in a tire circumferential direction. Thebelt layers 30 have belt cords extending to be inclined to thepredetermined direction which is an extending direction of the carcasscord. An exemplar belt used as the belt cord is a steel cord.

The multiple belt layers 30 include a first belt layer 31, a second beltlayer 32, a third belt layer 33 a fourth belt layer 34, a fifth beltlayer 35, and a sixth belt layer 36.

The first belt layer 31 is located outside the carcass layer 20 in thetire radial direction trd. The first belt layer 31 is located at theinnermost position among the multiple belt layers 30 in the tire radialdirection trd. The second belt layer 32 is located outside the firstbelt layer 31 in the tire radial direction trd. The third belt layer 33is located outside the second belt layer 32 in the tire radial directiontrd. The fourth belt layer 34 is located outside the third belt layer 33in the tire radial direction trd. The fifth belt layer 35 is locatedoutside the fourth belt layer 34 in the tire radial direction trd. Thesixth belt layer 36 is located outside the fifth belt layer 35 in thetire radial direction trd. The sixth belt layer 36 is located at theoutermost position among the multiple belt layers 30 in the tire radialdirection trd. The first belt layer 31, the second belt layer 32, thethird belt layer 33, the fourth belt layer 34, the fifth belt layer 35,and the sixth belt layer 36 are disposed from the inner side toward theouter side in the tire radial direction trd.

In this embodiment, widths of the first belt layer 31 and the secondbelt layer 32 each are 25% to 70%, both inclusive, of a width TW of thetread face 5 a in the tread width direction twd. Widths of the thirdbelt layer 33 and the fourth belt layer 34 each are 55% to 90%, bothinclusive, of the width TW of the tread face 5 a in the tread widthdirection twd. Widths of the fifth belt layer 35 and the sixth beltlayer 36 each are 60% to 110%, both inclusive, of the width TW of thetread face 5 a in the tread width direction twd.

In this embodiment, in the tread width direction twd, the width of thefifth belt layer 35 is larger than the width of the third belt layer 33,the width of the third belt layer 33 is equal to or larger than thewidth of the sixth belt layer 36, the width of the sixth belt layer 36is larger than the width of the fourth belt layer 34, the width of thefourth belt layer 34 is larger than the width of the first belt layer31, and the width of the first belt layer 31 is larger than the width ofthe second belt layer 32. In the tread width direction twd, the fifthbelt layer 35 has the largest width, and the second belt layer 32 hasthe smallest width among the multiple belt layers 30. Accordingly, themultiple belt layers 30 include the shortest belt layer having thesmallest length in the tread width direction twd (that is, the secondbelt layer 32).

The second belt layer 32 as the shortest belt layer has a belt end 30 ethat is an end in the tread width direction twd.

In this embodiment, inclined angles of the belt cords of the first beltlayer 31 and the second belt layer 32 to the carcass cord in the treadface view each are 70 degrees to 85 degrees, both inclusive. Inclinedangles of the belt cords of the third belt layer 33 and the fourth beltlayer 34 to the carcass cord each are 50 degrees to 75 degrees, bothinclusive. Inclined angles of the belt cords of the fifth belt layer 35and the sixth belt layer 36 to the carcass cord each are 50 degrees to70 degrees, both inclusive.

The multiple belt layers 30 include an inner crossing belt group 30A, anintermediate crossing belt group 30B, and an outer crossing belt group30C.

The inner crossing belt group 30A consists of a pair of belt layers 30,and is located outside the carcass layer 20 in the tire radial directiontrd. The inner crossing belt group 30A includes the first belt layer 31and the second belt layer 32. The intermediate crossing belt group 30Bconsists of a pair of belt layers 30, and is located outside the innercrossing belt group 30A in the tire radial direction trd. Theintermediate crossing belt group 30B includes the third belt layer 33and the fourth belt layer 34. The outer crossing belt group 30C consistsof a pair of belt layers 30, and is located outside the intermediatecrossing belt group 30B in the tire radial direction trd. The outercrossing belt group 30C includes the fifth belt layer 35 and the sixthbelt layer 36.

A width of the inner crossing belt group 30A is 25% to 70%, bothinclusive, of the width of the tread face 5 a in the tread widthdirection twd. A width of the intermediate crossing belt group 30B is55% to 90%, both inclusive, of the width of the tread face 5 a in thetread width direction twd. A width of the outer crossing belt group 30Cis 60% to 110%, both inclusive, of the width of the tread face 5 a inthe tread width direction twd.

An inclined angle of the belt cord of the inner crossing belt group 30Ato the carcass cord in the tread face view is 70 degrees to 85 degrees,both inclusive. An inclined angle of the belt cord of the intermediatecrossing belt group 30B to the carcass cord in the tread face view is 50degrees to 75 degrees, both inclusive. An inclined angle of the beltcord of the outer crossing belt group 30C to the carcass cord in thetread face view is 50 degrees to 70 degrees, both inclusive.

The inclined angle of the belt cord of the inner crossing belt group 30Ato the carcass cord in the tread face view is the largest. The inclinedangle of the belt cord of the intermediate crossing belt group 30B tothe carcass cord is equal to or larger than that of the outer crossingbelt group 30C.

As shown in FIGS. 1 and 2, the tread section 5 has multiple grooveportions (circumferential grooves 50) and multiple lateral grooveportions (lug grooves 60) that extend in a tire circumferentialdirection tcd. The tread section 5 also has multiple land portions(circumferential land portions 70) defined by the multiplecircumferential grooves 50 and the multiple lug grooves 60.

The multiple circumferential grooves 50 extend in the tirecircumferential direction tcd. The multiple circumferential grooves 50include circumferential grooves 50A, 50B, and 50C.

The circumferential groove 50A is a circumferential groove located atthe outermost position in the tread width direction twd. Thecircumferential groove 50C is located on the tire center line CL.

The circumferential groove 50B is located between the circumferentialgroove 50A and the circumferential groove 50C in the tread widthdirection twd. Specifically, the circumferential groove 50B is formedsuch that a length DL from the belt end 30 e to a groove center line WL,which passes the widthwise center of the circumferential groove 50B inthe tread face view of the tire, along the tread width direction twd isequal to or smaller than 200 mm.

As described below, a groove bottom 50B2 of the circumferential groove50B has multiple projection parts 500. Thus, the temperature around thetread section 5 in which the circumferential groove 50B is locateddecreases. Since the length DL from the belt end 30 e to the groovecenter line WL in the tread width direction twd is equal to or smallerthan 200 mm, the temperature of the belt end 30 e decreases. Suchtemperature drop suppresses deterioration of the rubber member aroundthe belt end 30 e due to heat, and thereby inhibits generated heat frompeeling the second belt layer 32 from the belt end 30 e as a startingpoint and the surrounding rubber member. Since the second belt layer 32as the shortest belt layer most susceptible to heat of the tread section5 is inhibited from being peeled off, the durability of the tire 1 canbe improved.

The tread section of the heavy-loading tire put on trucks, buses, andconstruction vehicles has a large rubber gauge (thickness) and a largerubber volume. When such heavy-loading tire is repeatedly deformed, thetemperature of the tread section rises. In such heavy-loading tire, inparticular, the tread section 5 located outer than the tread section 5near the tire center line CL in the tread width direction twd generatesmore heat. Thus, by providing the multiple projection parts 500 on thegroove bottom 50B2 of the circumferential groove 50B located outside thetire center line CL, heat can be effectively dissipated from the treadsection 5.

The lug grooves 60 extend from the circumferential groove 50B to thebuttress section 9. The lug grooves 60 have respective openings 60 a inthe buttress section 9. Accordingly, the lug grooves 60 are opened tothe tread end 5 e. The lug grooves 60 communicate with thecircumferential groove 50A and the circumferential groove 50B. Innerends of the lug grooves 60 in the tread width direction twd communicatewith the circumferential groove 50B.

A width between both ends (tread ends 5 e) of the tread section 5 in thetread width direction is expressed as TW. In this embodiment, both endsof the tread section 5 refer to both ends, in the tread width directiontwd, of a contact range where the tire is in contact with the roadsurface. The state where the tire is in contact with the road surfacemeans the state where the tire is attached to the normal rim, andreceives the normal internal pressure and the normal load.

In the tread face view of the tire 1, the lug grooves 60 extend to beinclined to the tread width direction twd. An inclined angle φ of thelug grooves 60 to the tread width direction twd is 15 degrees to 60degrees, both inclusive.

As shown in FIG. 1, when the tire 1 rotates in the rotation directiontr1, an air flow (relative wind) in the direction opposite to therotation direction tr1 is generated in response to the rotation of thetire 1. The left lug grooves 60 in FIG. 1 move forward in the rotationdirection tr1 as they are located outward in the tread width directiontwd. The inclined angle φ of the lug grooves 60 to the tread widthdirection twd is 15 degrees to 60 degrees, both inclusive. For thisreason, when the tire 1 rotates in the rotation direction tr1, an airflow entering the lug grooves 60 from the outside can be inhibited fromhitting the side walls of the lug grooves 60 near the openings 60 a andstaying there. This can improve the thermal conductivity of the luggrooves 60, and smoothly guide the air flow to the circumferentialgroove 50B, and therefore lower the temperature of the tread section 5.

On the other side, when the tire 1 rotates in the rotation directiontr1, in the right side of the tread section 5 in FIG. 1, an air flow(relative wind) in the direction opposite to the rotation direction tr1is generated in response to the rotation of the tire 1. Since theinclined angle φ of the lug grooves 60 to the tread width direction twdis 15 degrees to 60 degrees, both inclusive, air in the lug grooves 60easily flows along the lug grooves 60. As a result, discharging of airto the outer side from the lug grooves 60 in the tread width directiontwd can be promoted to increase the flow rate of the air flowing in thelug grooves 60. This can also improve the thermal conductivity of thelug grooves 60, lowering the temperature of the tread section 5.

Air flowing in the circumferential groove 50B more easily enters the luggrooves 60. Air that passes through the circumferential groove 50B andstores heat flows to the outside through the lug grooves 60, promotingdissipation of heat from the tread section 5.

The inclined angle φ of 60 degrees or less can ensure the stiffness ofbelow-mentioned land blocks 100 and 200. This can suppress deformationof the land blocks 100 and 200 due to the rotation of the tire 1, andaccordingly suppress an increase of the heating value of the treadsection 5.

The multiple circumferential land portions 70 extend in the tirecircumferential direction. The multiple circumferential land portions 70include circumferential land portions 70A, 70B, and 70C.

The circumferential land portion 70A is a circumferential land portionlocated at the outermost position in the tread width direction twd. Thecircumferential land portion 70B is located between the circumferentialland portion 70A and the circumferential land portion 70C in the treadwidth direction twd. The circumferential land portion 70C is acircumferential land portion located at the innermost position in thetread width direction twd.

The circumferential land portion 70A and the circumferential landportion 70B have the lug grooves 60. The tread section 5 is providedwith land blocks 100 and 200 defined by the lug grooves 60. That is, thecircumferential land portion 70A is divided by the lug grooves 60 toform the land block 100. The circumferential land portion 70B is dividedby the lug grooves 60 to form the land block 200.

In this embodiment, the tire 1 is assumed as a radial tire having anoblateness of 80% or less, a rim diameter of 57″ or more, a loadcapacity of 60 metric ton or more, and a load factor (k-factor) of 1.7or more, for example. It should be noted that the tire 1 is not limitedto this.

(2) Structure Outline of Air Supply Mechanism

Structure outline of the air supply mechanism according to thisembodiment will be described with reference to FIG. 1 to FIG. 4. FIG. 3is an enlarged perspective view of the land block 100. FIG. 4 is a planview of the circumferential land portion 70A in the tread face view.

In the tire 1, the lateral groove portions (lug grooves 60) are providedwith respective air supply mechanisms for air supply. In thisembodiment, the air supply mechanisms each are formed of a tapered face100R.

As shown in FIG. 1 to FIG. 4, the land block 100 has a tread face 100Sthat comes into contact with the road surface, a side face 101 formedoutside the land block 100 in the tread width direction twd, a side face102 formed inside the land block 100 in the tread width direction twd, alateral groove face 103 that constitutes a groove wall of the lug groove60 formed on one side of the land block 100 in the tire circumferentialdirection tcd, and a lateral groove face 104 that constitutes a groovewall of the lug groove 60 formed on the other side of the land block 100in the tire circumferential direction tcd. The land block 100 has thetapered face 100R that crosses the tread face 100S, the side face 101,and the lateral groove face 103 at a corner portion 100A formed by thetread face 100S, the side face 101, and the lateral groove face 103. Thecorner portion 100A constitutes the above-mentioned tread end 5 e of thetread section 5.

The side face 101 is formed in the land block 100 near the buttresssection 9. The side face 101 extends in the tire circumferentialdirection tcd. The side face 101 is connected to the lateral groovefaces 103 and 104 of the land block 100, which form the groove walls ofthe lug grooves 60. The side face 102 faces the side face 101 in thetread width direction twd. The side face 102 forms a groove wall of thecircumferential groove 50A adjacent to the inner side of the land block100 in the tread width direction twd.

The lateral groove face 103 extends in the tread width direction twd.The lateral groove face 103 is located on one side of the land block 100in the tire circumferential direction tcd. The lateral groove face 104extends in the tread width direction twd. The lateral groove face 104 islocated on the other side of the land block 100 in the tirecircumferential direction tcd.

Each tapered face 100R extends in the tire circumferential direction tcdat the corner portion 100A formed by the tread face 100S and the sideface 101. The tapered face 100R is inclined inward in the tire radialdirection trd in the cross section of the land block 100 in the tirecircumferential direction tcd and the tire radial direction trd, as itgets closer to one side in the tire circumferential direction tcd. Thetapered face 100R is also inclined inward in the tire radial directiontrd in the cross section of the land block 100 in the tread widthdirection twd and the tire radial direction trd, as it gets closer tothe outer side in the tread width direction twd.

That is, the tapered face 100R is chamfered at a vertex of the treadface 100S, the side face 101, and the lateral groove face 103. In otherwords, the tapered face 100R is formed to have at least one side on eachof the tread face 100S, the side face 101, and the lateral groove face103.

The tapered face 100R has one side on the side face 101, and does nothave one side on the side face 102, out of the side face 101 and theside face 102 of the land block 100 in the tread width direction twd.That is, in the land block 100, one (side face 102) of the side face 101and the side face 102, which are opposed to each other in the treadwidth direction twd, does not cross the tapered face 100R.

Further, the tapered face 100R has one side on the lateral groove face103 and does not have one side on the lateral groove face 104, out ofthe lateral groove face 103 and the lateral groove face 104 of the landblock 100 in the tire circumferential direction tcd. That is, one(lateral groove face 104) of the lateral groove face 103 and the lateralgroove face 104, which are opposed to each other in the land block 100in the tire circumferential direction tcd, does not cross the taperedface 100R.

Forming the tapered face 100R as described above facilitates air flowingalong the tapered face 100R during rotation of the tire 1 to hit againstthe lateral groove face 104 of another land block 100 adjacent in thetire circumferential direction tcd. That is, air flowing along thetapered face 100R is easily taken into the lug groove 60 of the landblock 100 adjacent in the tire circumferential direction tcd.

In this embodiment, the tapered face 100R is planar. That is, thetapered face 100R linearly extends on the cross section in the tirecircumferential direction tcd and the tire radial direction trd, or thecross section in the tread width direction twd and the tire radialdirection trd.

As shown in FIG. 3, in the case of a plane Sv passing a vertex P2 of thetapered face 100R, the tread face 100S, and the side face 101, a vertexP1 of the tapered face 100R, the tread face 100S, and the lateral grooveface 103, and a vertex P3 of the tapered face 100R, the side face 101,and the lateral groove face 103, an angle θ2 that the plane Sv formswith the tread face 100S is larger than 0 degree and smaller than 45degrees. Alternatively, an angle θ1 that the plane Sv forms with theside face 101 is larger than 0 degree and smaller than 45 degrees. Thatis, one of the angle θ1 or the angle θ2 only needs to be larger than 0degree and smaller than 45 degrees. More preferably, the angle θ1 (orthe angle θ2) is larger than 10 degrees and smaller than 30 degrees. Inthis embodiment, the tapered face 100R is planar and thus, the taperedface 100R is the same as the plane Sv.

Preferably, the tapered face 100R is formed such that a distance L2between the vertex P1 and the vertex P3 in the tire radial direction trdis larger than a distance L1 between the vertex P1 and the vertex P2 inthe tread width direction twd. The reason for this is as follows: sincethe distance L2 is larger than the distance L1, even when wear of theland block 100 occurs from the tread face 100S, the tapered face 100Rtends to remain. That is, the effect of the tapered face 100R can last.More preferably, the distance L2 is 50 mm or more.

In the tire 1, the land block 100 has the tapered face 100R that crossesthe tread face 100S, the side face 101, and the lateral groove face 103at the corner portion 100A formed by the tread face 100S and the sideface 101 located outside in the tread width direction twd.

Thus, as shown in FIG. 4, when the tire 1 rotates in the rotationdirection tr1, an air flow (relative wind) AR generated by the rotationof the tire 1 flows along the tapered face 100R in the directionopposite to the rotation direction tr1. The air flow AR flowing alongthe tapered face 100R hits against the lateral groove face 104 of theland block 100 located behind in the rotation direction tr1, and isguided to the lug groove 60. As a result, the air flow AR from the sideface 101 of the land block 100 to the lug groove 60 is formed. That is,air around the tire 1 is taken into the lug groove 60 to increase theflow rate of air flowing in the lug groove 60. This can improve thethermal conductivity of the lug grooves 60, lowering the temperature ofthe tread section 5.

When the tire 1 rotates in a rotation direction tr2, an air flow(relative wind) AR generated in the lug groove 60 due to the rotation ofthe tire 1 flows out along the tapered face 100R in the directionopposite to the rotation direction tr2. This promotes discharging of airto the outer side in the tread width direction twd through the luggroove 60, increasing the flow rate of air flowing in the lug groove 60.This can improve the thermal conductivity of the lug grooves 60,lowering the temperature of the tread section 5.

(3) Structure Outline of Recess Portion 300

Structure outline of a recess portion 300 according to this embodimentwill be described with reference to FIG. 5. FIG. 5(a) to FIG. 5(c) areenlarged plan views illustrating the recess portion 300 in the treadface view.

As shown in FIG. 5(a) to FIG. 5(c), the circumferential land portion 70Chas the recess portion 300. The recess portion 300 is located in theextending direction of the lug groove 60. The recess portion 300 isformed in the groove wall face of the circumferential land portion 70Copposed to the lug groove 60.

In this embodiment, the recess portion 300 is triangular in the treadface view. In the tread face view, one wall face 300 a of the recessportion 300 extends along an extension line of one wall face of the luggroove 60, and the other wall face 300 b of the recess portion 300crosses an extension line of the other wall face of the lug groove 60.In the tread face view, an intersection of the groove wall face of thecircumferential land portion 70C opposed to the lug groove 60 with theextension line of the one wall face of the lug groove 60 is anintersection a, and an intersection of the groove wall face of thecircumferential land portion 70C opposed to the lug groove 60 with theextension line of the other wall face of the lug groove 60 is anintersection b. In the tread face view, an end A of the wall face 300 anear the circumferential groove 50B and the intersection a are locatedat the same position, and an end B of the wall face 300 b near thecircumferential groove 50B and the intersection b are located atdifferent positions. The end B is not located between the intersection aand the intersection b. Accordingly, a length from the end A to the endB is larger than a length from the intersection a to the intersection b.In the tread face view, a contact point between the wall face 300 a andthe wall face 300 b is a vertex C.

In the tread face view, an angle that the extension line along thegroove wall face of the circumferential land portion 70C opposed to thelug groove 60 forms with the wall face 300 a is an angle α, and an anglethat extension line along the groove wall face of the circumferentialland portion 70C opposed to the lug groove 60 forms with the wall face300 b is an angle β. In this embodiment, the angle β is smaller than theangle α. Preferably, α satisfies 20≦α≦70, and β satisfies β≦45 degrees.

The recess portion 300 is formed such that the center of the recessportion 300 on the extending direction of the circumferential groove 50Bis displaced from the extending direction of the lug groove 60 and therug groove center line passing the center in the direction orthogonal tothe extending direction. The center of the recess portion 300 refers toat least one of the center of a line connecting the end A to the end B,and the vertex C.

As shown in FIG. 5(b), a length 300W of the recess portion 300 in thetread width direction twd varies along the tire circumferentialdirection tcd. That is, the length 300W gradually increases from the endB toward the vertex C in the tire circumferential direction tcd. Thelength 300W gradually decreases from the end C to a vertex A in the tirecircumferential direction tcd.

A length 300L of the recess portion 300 in the tire circumferentialdirection tcd gradually decreases from the side opened to thecircumferential groove 50B to the back. That is, the length 300L has alargest distance between the end A and the end B, and graduallydecreases toward the vertex.

As shown in FIG. 5(c), by forming the recess portion 300, the air flowAR flowing through the lug groove 60 from the outer side to the innerside in the tread width direction twd hits against the wall face 300 bof the recess portion 300. In FIG. 5(c), since the wall face 300 a islocated above the wall face 300 b, the air flow AR is hard to flow abovethe wall face 300 b. Thus, the air flow AR smoothly flows under guide ofthe circumferential groove 50B.

Since the recess portion 300 is formed to generate the air flow AR inone direction of the tire circumferential direction tcd, the air flow ARhardly stays in the circumferential groove 50B. This can improve thethermal conductivity of the circumferential groove 50B, lowering thetemperature of the tread section 5.

(4) Structure Outline of Projection Parts 500 (4.1) Projection Parts 500

Structure outline of the projection parts 500 according to thisembodiment will be described with reference to FIG. 6 to FIG. 9.

FIG. 6 is a partial cutaway perspective view illustrating thecircumferential groove 50B. FIG. 7 shows the shape of thecircumferential groove 50B in the tread face view (when viewed fromabove the tread section 5). FIG. 8 shows the shape of thecircumferential groove 50B when viewed from a direction of F5 in FIG. 7.FIG. 9 is a sectional view illustrating the circumferential groove 50B(projection part 500) taken along a line F6-F6 in FIG. 7.

As shown in FIG. 6 to FIG. 9, the groove bottom 50B2 of thecircumferential groove 50B is provided with the multiple projectionparts 500.

In this embodiment, the projection parts 500 are arranged atpredetermined intervals P in the circumferential groove 50B. Inaddition, the projection parts 500 extend from one side wall 50B1 of theside walls 50B1 and 50B3 forming the circumferential groove 50B to theother side wall 50B3. The projection parts 500 are provided away fromthe side wall 50B1 and the side wall 50B3. In this embodiment, eachprojection part 500 includes a projection end 500 e 1 and a projectionend 500 e 2 which are ends in the extending direction x of theprojection part 500 in the tread face view. The projection end 500 e 1and the projection end 500 e 2 are away from the side wall 50B1 and theside wall 50B3. Specifically, in the tread face view, spaces areprovided between the side wall 50B1 and the projection end 500 e 1 andbetween the side wall 50B3 and the projection end 500 e 2. In thisembodiment, the side wall 50B1 and the side wall 50B3 extendsubstantially in parallel with the tire circumferential direction, andthe side wall 50B1 and the side wall 50B3 are formed to be opposed toeach other.

The projection parts 500 each are provided to erect outward in the tireradial direction from the groove bottom 50B2 of the circumferentialgroove 50B. In this embodiment, the projection parts 500 are flatplate-like rubbers erected from the groove bottom 50B2, and are inclinedto the tire circumferential direction.

Specifically, as shown in FIG. 7, an angle θf that the groove centerline WL forms with the projection part 500 is 10 degrees to 60 degrees,both inclusive. The angle θf is an angle that the extending direction xof the projection parts 500 forms with the groove center line WL passingthe center of the circumferential groove 50B in the width direction inthe tread face view of the tire 1, and that is formed opposite to therotation direction of the tire 1. That is, the angle θf is formed on theadvancing side of the air flow AR generated by the rotation of the tire1 in the rotation direction tr1.

Given that the length of the projection parts 500 along the groovecenter line WL is L and the predetermined intervals are P in the treadface view of the tire 1, the projection parts 500 provided on thecircumferential groove 50B each satisfy a relationship of 0.75 L≦P≦10 L.

Since the projection parts 500 each satisfy the relationship of 0.75L≦P, the number of the projection parts 500 provided in thecircumferential groove 50B does not become too large, which inhibitsdeceleration of air flowing in the circumferential groove 50B. Since theprojection parts 500 each satisfy the relationship of P≦10 L, the numberof the projection parts 500 provided on circumferential groove 50B doesnot become too small, and the air flow AR1 efficiently changes to aspiral flow (swirling flow).

Preferably, a relationship of 1.25 L<P is satisfied. More preferably, arelationship of 1.5 L<P is satisfied, and still more preferably, arelationship of 2.0 L<P is satisfied. Through satisfaction of theserelations, the number of the projection parts 500 provided oncircumferential groove 50B becomes more proper. The area of the groovebottom 50B2, through which the air flow AR passes, does not become toosmall, efficiently dissipating heat from the groove bottom 50B2.

A length L is a length from one end to the other end of the projectionpart 500 in an extending direction ged of the circumferential groove 50B(in this embodiment, tire circumferential direction). The interval P isa distance between centers of the projection parts 500 at which theprojection parts 500 cross the groove center line WL.

Given that a distance between the side wall 50B1 to the side wall 50B3of the circumferential groove 50B is the groove width W, the length Lcan be also expressed as W/tan θf+TWf/sin θf. As shown in FIG. 9, aprojection width TWf is a width of the projection part 500 in thelateral direction of the projection part 500, that is, a width of theprojection part 500 in the direction orthogonal to the extendingdirection x.

In addition, in the tread face view, the projection part 500 satisfies arelationship of 0.4≦FW/W<1, where FW denotes a length of the projectionpart 500 in an orthogonal direction which is orthogonal to the extendingdirection ged of the circumferential groove 50B. In other words, thelength FW of the projection part 500 is shorter than the groove width W.Then, the length FW of the projection part 500 is 0.4 or more times thegroove width W of the circumferential groove 50B.

In this embodiment, since the circumferential groove 50B extends alongthe tire circumferential direction tcd, the length FW is equal to thelength of the projection part 500 in the tread width direction twd. Thelength FW is a length from the projection end 500 e 1 on one side to theprojection end 500 e 2 on the other side on a plane on which theprojection part 500 is projected when viewed from the extendingdirection ged of the circumferential groove 50B, the plane beingorthogonal to the extending direction ged of the circumferential groove50B.

Moreover, as shown in FIG. 8, given that a height of the projection part500 from the groove bottom 50B2 is Hf, and a depth of thecircumferential groove 50B from the tread face 5 a to the groove bottom50B2 (deepest portion) is D, the projection part 500 satisfies arelationship of 0.03 D<Hf≦0.6 D. Given that the groove width of thecircumferential groove 50B is W, the groove bottom 50B2 is flat at leastover the width of 0.2 W. That is, the central portion in the groovewidth W of the groove bottom 50B2 including the groove center line WLhas a flat and smooth surface of the groove bottom 50B2 with noirregularity.

Given that the groove width of the circumferential groove 50B is W, andthe width of the projection part 500 in the direction orthogonal to theextending direction x of the projection part 500 is TWf, the projectionpart 500 satisfies a relationship of TWf/cos θf≦0.9 W. Preferably, theprojection parts 500 are provided so as to satisfy a relationship of0.2≦TWf. Satisfying the relationship of 0.2≦TWf can ensure theprojection width TWf, improving the durability of the projection parts500. As a result, the projection parts 500 can be inhibited from beingdamaged during use of the tire 1, which enables effective suppression ofa temperature rise of the tread section 5 during driving of the vehicle.

For example, the length L is the range of 10 mm to 100 mm. For example,the interval P is 1.25 mm to 4.00 mm. For example, the projection heightHf is 5 mm to 15 mm. For example, the projection width TWf is 0.5 mm to10 mm. For example, the depth D is 40 mm to 120 mm. For example, thegroove width W of the groove bottom 50B2 is 5 mm to 20 mm.

(4.2) Modification Example of Projection Part 500

A modification example of projection parts 500 will be described withreference to FIG. 10 and FIG. 11.

FIG. 10 is a view illustrating a shape of a circumferential groove 50Bin a tread face view according to the modification example. FIG. 11 is aview illustrating a shape of the circumferential groove 50B viewed froman F7 direction in FIG. 10.

As shown in FIG. 10 and FIG. 11, the projection parts 500 are eachseparated into plural projection segments in a tread face view. In thismodification example, the projection part 500 includes a firstprojection segment 500 a and a second projection segment 500 b. In otherwords, the projection part 500 is separated into the first projectionsegment 500 a and the second projection segment 500 b. The projectionpart 500 is separated in the extending direction x of the projectionpart 500. In the tread face view, the projection part 500 is providedwith an opening which is formed in the center of the projection part 500in the extending direction x of the projection part 500.

The first projection segment 500 a includes a first projection end 500 e3. The first projection end 500 e 3 is an end on a widthwise center sideof the circumferential groove 50B. The other end of the first projectionsegment 500 a is continued to the side wall 501.

The second projection segment 500 b includes a second projection end 500e 4. The second projection end 500 e 4 is an end on the widthwise centerside of the circumferential groove 50B. The other end of the secondprojection segment 500 b is continued to the side wall 50B3.

As shown in FIG. 11, in this modification example, FW1 denotes a lengthof the first projection segment 500 a and FW2 denotes a length of thesecond projection segment 500 b. In the case where the projection part500 is separated into plural segments as in this modification example,the length FW is a total length of the plural projection segments. Inthis modification example, the length FW is a sum of the length FW1 andthe length FW2. In other words, the projection part 500 satisfies arelationship of 0.4≦(FW1+FW2)/W<1 in this modification example.

(5) Actions and Effects

In the tire 1, the groove bottom 50B2 of the circumferential groove 50Bis provided with the multiple projection parts 500, the projection parts500 extend from the one side wall 50B1 to the other side wall 50B3opposed to the one side wall 50B1, the side walls forming thecircumferential groove 50B, the projection part 500 are provided atpredetermined intervals on the circumferential groove 50B, and satisfythe relationship of 0.75 L≦P≦10 L and the relationship of 0.4≦FW/W<1.

The air flows AR1 and AR2 (relative wind) are generated in thecircumferential groove 50B in the opposite direction to the rotationdirection tr1 by rotation of the tire 1. As shown in FIG. 12(a) and FIG.12(b), the air flow AR1 along the side wall 50B3 located on one end sideof the projection part 500 which is a downstream side in the air flowingdirection is stopped from flowing along the circumferential groove 50Bbecause the projection part 500 stands in the way of the air flow, buttherefore proceeds while being inclined to the extending direction ofthe circumferential groove 50B and then climbs over the projection parts500. As a result, the air flow AR1 changes to a spiral flow (swirlingflow). Since the air flow proceeds while involving surrounding air, theflow rate of air increases, and the rate of the air flow AR1 alsoincreases. This facilitates heat dissipation from the tread section 5.

The air flow AR2 along the side wall 50B1 located on another end side ofthe projection part 500 which is an upstream side in the air flowingdirection proceeds in the extending direction of the projection parts500. Then, the air flow AR2 flows out of the circumferential groove 50Baround the other side wall 50B3 of the circumferential groove 50B. Airthat stores heat by passing through the circumferential groove 50B flowsto the outside, and thereby promotes heat dissipation from the treadsection 5.

Since the projection parts 500 each satisfy the relationship of 0.75L≦P, the number of the projection parts 500 provided on thecircumferential groove 50B does not become too large, which inhibitsdeceleration of air flowing through the circumferential groove 50B.Since the projection parts 500 each satisfy the relationship of P≦10 L,the number of the projection parts 500 provided on the circumferentialgroove 50B does not become too small, and the air flow AR1 efficientlychanges to a spiral flow (swirling flow). This facilitates heatdissipation from the tread section 5.

When the tread face 5 a comes into contact with the road surface, arubber member constituting the tread section 5 is deformed. Thisdeformation of the rubber member makes the groove width W of thecircumferential groove 50B deformed. For this reason, if the projectionpart is continued from the side wall 50B1 and the side wall 50B3, theprojection part tends to be damaged because stress acts on theprojection part (in particular, the ends of the projection part in theextending direction of the projection part).

The projection parts 500 each satisfy the relationship of FW/W<1. Inother words, the projection part 500 is separated into segments, or isseparated from the side wall 50B1 (and/or the side wall 50B3) of thecircumferential groove 50B. Such separation enables the stress whichwould otherwise act on the projection part 500 to be released from theprojection end 500 e 1 and the projection end 500 e 2, and thereby makesit less likely to damage the projection part 500.

Moreover, the projection parts 500 each satisfy the relationship of0.4≦FW/W. This can ensure a ground contact area of the projection parts500 and the groove bottom 50B2, so that the projection parts 500 can beinhibited from being damaged even when receiving external force appliedby a stone or the like.

Hence, satisfying the relationship of 0.4≦FW/W<1, the projection parts500 achieve improvement in durability. The improvement in the durabilityof the projection parts 500 results in reduction of damage of theprojection parts 500 during use of the tire, and thereby enables theprojection parts 500 to maintain their effect of dissipating heat fromthe tread section 5.

As a result, the tread section 5 is efficiently cooled, whicheffectively suppresses a temperature rise of the tread section 5 duringdriving of the vehicle.

Preferably, a relationship of 1.25 L<P is satisfied. Throughsatisfaction of the relation, the number of the projection parts 500provided on circumferential groove 50B becomes more proper. The area ofthe groove bottom 50B2, through which the air flow AR passes, does notbecome too small, efficiently dissipating heat from the groove bottom50B2.

Preferably, the angle θf that the extending direction of the projectionparts 500 forms with the groove center line WL is 10 degrees to 60degrees, both inclusive. Since the angle θf is equal to or larger than10 degrees, the acute angled portions formed by the projection parts 500and the side wall 50B1 (or side wall 50B3) can inhibit the air flow ARflowing through the circumferential groove 50B from becoming weak. Theprojection parts 500 can be easily formed on the circumferential groove50B. Since the angle θf is equal to or smaller than 60 degrees, the airflow AR2 flowing through the circumferential groove 50B can beefficiently changed to a spiral flow. This increases the flow ratepassing the groove bottom 50B2, achieving efficient heart dissipationfrom the tread section 5.

Preferably, a relationship of 0.03 D<Hf≦0.6 D is satisfied. Satisfyingthe relationship of 0.03 D<Hf, the height Hf of the projection parts 500is a predetermined height or more, and the projection parts 500 canefficiently change the air flow AR2 flowing through the circumferentialgroove 50B to a spiral flow. This increases the amount of flow passingthe groove bottom 50B2, and achieves efficient heat dissipation from thetread section 5. Satisfying the relationship of Hf≦0.6 D makes it morelikely to cause the spiral air flow AR1 to reach the groove bottom 50B2.As a result, heat is efficiently dissipated from the groove bottom 50B2.

The groove bottom 50B2 is flat at least over the width of 0.2 W. Thus,the air flow AR passing the groove bottom 50B2 is not obstructed, whichmakes it possible to more effectively suppress a temperature rise in thetread section 5.

Preferably, a relationship of DC/OD≧0.015 is satisfied. In the tire thatsatisfies the relationship of DC/OD≧0.015, the tread section 5 has alarger rubber gauge and therefore tends to store heat in the treadsection 5. For this reason, in the tire that satisfies the relationshipof DC/OD≧0.015, effective suppression of a temperature rise in the treadsection 5 during driving of the vehicle results in inhibition of anyfailure due to the temperature rise in the tread section 5. In addition,since the rubber gauge of the tread section 5 is large, the rubbermember forming the tread section 5 can be greatly deformed. Thus, in thetire that satisfies the relationship of DC/OD≧0.015, improvement in thedurability of the projection parts 500 also results in inhibition of anyfailure due to a temperature rise of the tread section 5.

The projection parts 500 continuously extend from the one side wall 50B1to the other side wall 50B3. Accordingly, the air flow AR1 proceedingalong the projection parts 500 can climb over the projection parts 500near the side wall 50B3 and thus efficiently changes to a spiral flow(swirling flow). This can achieve efficient heat dissipation from thetread section 5.

(6) Comparative Evaluation

To confirm the effects of the tire according to the present invention,following measurement was made. The present invention is not limited toa following operating example.

A tire (59/80R63) for mine was used as a test tire. Projection partswere provided on a circumferential groove of the tire, and the thermalconductivity at the tire rotational speed of 20 km/h was measured whilean angle θf formed by the groove center line and the projection parts, acoefficient as a multiplier of the length L, and a coefficient as amultiplier of the groove depth D were varied. The thermal conductivityin the absence of the projection parts was defined as 100, and wascompared with measured thermal conductivity. FIG. 13 to FIG. 15 showresults. FIG. 13 shows a relationship between the angle θf and thethermal conductivity of the circumferential groove (represented inindex). FIG. 14 shows a relationship between the coefficient as amultiplier of the length L of the projection parts and the thermalconductivity of the circumferential groove. FIG. 15 shows a relationshipbetween the coefficient as a multiplier of the groove depth D and thethermal conductivity of the circumferential groove.

FIG. 13 demonstrates that the angle φ of 10 degrees to 60 degrees, bothinclusive, achieved a favorable thermal conductivity. Especially theangle θf of 15 degrees to 40 degrees, both inclusive, achieved a morefavorable thermal conductivity.

FIG. 14 demonstrates that the coefficient as a multiplier of the lengthL of 0.75 to 10, both inclusive, achieved a favorable thermalconductivity. The coefficient as a multiplier of the length L of 1.25 ormore achieved a more favorable thermal conductivity. The coefficient asa multiplier of the length L of 1.5 to 7, both inclusive, achieved astill more favorable thermal conductivity.

FIG. 15 demonstrates that the coefficient as a multiplier of the groovedepth D of 0.03 to 0.4, both inclusive, achieved a favorable thermalconductivity.

Next, by preparing and using the above-mentioned tire, followingevaluations was made, in which durability of the projection parts oftires of Operating examples 1 to 12 and Comparative examples 1 to 4 wasevaluated.

In all of tires of Operating examples and Comparative examples, thethickness of a tread gauge in the tire radial direction trd was 140 mm,the depth of the circumferential groove in the tire radial direction trdwas 70 mm, and the width of the circumferential groove in the treadwidth direction was 10 mm. The groove bottom of the circumferentialgroove was provided with projection parts. The angle θf of theprojection parts was 20 degrees, and the interval P between theprojection parts was 1.25 times the length L of the projection parts 500along the groove center line WL, and the height Hf of the projectionparts was 0.1 times the groove depth D of the circumferential groove.

The tire of Comparative example 1 was provided with projection partseach continued from one side wall to the other side wall of thecircumferential groove.

The tires of Comparative example 2 and Operating examples 1 to 6 wereeach provided with projection parts according to the foregoingembodiment (projection parts of an A type). To be specific, eachprojection part was provided away from the one side wall and the otherside wall.

The tires of Comparative example 3 and Operating examples 7 to 12 wereeach provided with projection parts according to the foregoingmodification example (projection parts of a B type). To be specific,each projection part was separated into segments in the extendingdirection of the projection part.

The tire of Comparative example 4 was provided with no projection parts.

The tire of Comparative example 1 had a FW/W value of 1.0. The tire ofComparative example 2 had a FW/W value of 0.3. The tire of Comparativeexample 3 had a FW/W value of 0.3.

The tire of Operating example 1 had a FW/W value of 0.9. The tire ofOperating example 2 had a FW/W value of 0.8. The tire of Operatingexample 3 had a FW/W value of 0.7. The tire of Operating example 4 had aFW/W value of 0.6. The tire of Operating example 5 had a FW/W value of0.5. The tire of Operating example 6 had a FW/W value of 0.4. The tireof Operating example 7 had a FW/W value of 0.9. The tire of Operatingexample 8 had a FW/W value of 0.8. The tire of Operating example 9 had aFW/W value of 0.7. The tire of Operating example 10 had a FW/W value of0.6. The tire of Operating example 11 had a FW/W value of 0.5. The tireof Operating example 12 had a FW/W value of 0.4.

Table 1 shows results. Note that, using the durability of the projectionparts in Comparative example 1 as a reference (100), the durability ofthe projection parts in the other examples is expressed in index. Then,using the thermal conductivity of the projection parts in Comparativeexample 4 as a reference (100), the thermal conductivity of theprojection parts in the other examples is expressed in index.

TABLE 1 Durability Projection of Thermal Type FW/W ProjectionConductivity Comparative example 1 — 1 100 110 Operating example 1 A 0.9109 121 Operating example 2 A 0.8 107 120 Operating example 3 A 0.7 106119 Operating example 4 A 0.6 104 115 Operating example 5 A 0.5 103 113Operating example 6 A 0.4 102 112 Comparative example 2 A 0.3 99 109Operating example 7 B 0.9 106 119 Operating example 8 B 0.8 105 116Operating example 9 B 0.7 104 115 Operating example 10 B 0.6 103 114Operating example 11 B 0.5 102 112 Operating example 12 B 0.4 101 111Comparative example 3 B 0.3 97 107 Comparative example 4 — — — 100

As shown in Table 1, it was observed that the projection parts of thetires in Operating examples achieved better durability than theprojection parts of the tires in Comparative examples. Hence, it wasconfirmed that the durability of the projection parts is improved whenthe relationship of 0.4≦FW/W<1 is satisfied.

In addition, it was observed that the durability of the projection partsof the A type is improved more when the relationship of 0.7≦FW/W<1 issatisfied. Then, it was observed that the durability of the projectionparts of the B type is improved more when the relationship of 0.8≦FW/W<1is satisfied.

Moreover, as shown in Table 1, it was found that the thermalconductivity of the tires in Operating examples is better than that ofthe tires in Comparative examples. Hence, it was confirmed that atemperature rise of the tread section during driving of a vehicle can beeffectively suppressed by using the tire according to the presentinvention.

(7) Other Embodiments

Although the present invention has been described with reference to theembodiment of the present invention, it should not be understood thatthe description and figures that form a part of this disclosure limitthe present invention. The present invention includes variousembodiments that are not described herein.

Following embodiments can be appropriately combined with theabove-mentioned embodiment so as not to impair effects of the invention.

(7.1) Air Supply Mechanism

Although the air supply mechanism is formed of the tapered face 100R inthe above-mentioned embodiment, the air supply mechanism is not limitedto the tapered face.

For example, as shown in FIGS. 16 and 17, the length of the land block100 in the tread width direction twd may become smaller from one sidetoward the other side in the tire circumferential direction tcd.

FIG. 16 is a plan view illustrating a circumferential land portion 70Ain accordance with another embodiment in the tread face view.

A one end 100D of the land block 100 in the tire circumferentialdirection tcd is located on the rear side in the rotation direction tr1in which the vehicle to which the tire 1 is attached advances. The otherend 100E of the land block 100 in the tire circumferential direction tcdis located on the front side in the rotation direction tr1. A length La1of the end 100D in the tread width direction is smaller than a lengthLa2 of the end 100E of the land block 100 in the tread width direction.A difference between the length Lb1 and the length La1 is expressed as alength Lw1, and the length Lw1 is preferably 5 mm or more.

The side face 101 extends while being inclined toward the inner side ofthe land block 100 from the plane along the tire circumferentialdirection, and extends continuously to the lateral groove face 103 ofthe land block 100, which forms the inner wall of the lug groove 60. Theend 100D of the land block 100 in the tire circumferential directiontcd, which is located on the rear side in the rotation direction, islocated inner from the side wall section 7 by the length Lw1 in thetread width direction twd. That is, the rear side of the buttresssection 9 in the rotation direction in the tire circumferentialdirection tcd of the land block 100 is located inner from the side wallsection 7 by the length Lw in the tread width direction twd. For thisreason, a step is formed between the buttress section 9 and the sideface 101. A groove bottom 60 b that is the groove bottom of the luggroove 60 extends from the end 100D in the tire circumferentialdirection tcd, which is located on the rear side in the rotationdirection, toward the end 100E. The groove bottom 60 b is locatedbetween the buttress section 9 and the side face 101.

As shown in FIG. 16, when the tire 1 rotates in the rotation directiontr1, an air flow (relative wind) AR generated by the rotation of thetire 1 flows along the side face 101 of the land block 100 in thedirection opposite to the rotation direction tr1. The air flow ARflowing along the side face 101 hits against the lateral groove face 104of the land block 100 located behind in the rotation direction tr1, andis guided to the lug groove 60. As a result, air around the tire 1 istaken into the lug groove 60 to increase the flow rate of air flowing inthe lug groove 60. This can improve the thermal conductivity of the luggroove 60, lowering the temperature of the tread section 5.

FIG. 17 is a plan view illustrating the circumferential land portion 70Ain accordance with another embodiment in the tread face view. A curvedround face 100Ru is formed at a vertex of the tread face 100S of thetread section 5 to come into contact with the road surface, the sideface 101, and the lateral groove face 103, in the land block 100 of thetire 1. That is, the tread face 100S, the side face 101, and the lateralgroove face 103 are chamfered. As shown in FIG. 17, an area of the treadface 100S of the tread section 5 to come into contact with the roadsurface in the land block 100 of the tire 1 is smaller than an area ofthe land block 100 continuous to the groove bottom 60 b of the luggroove 60. The land block 100 gradually becomes larger from the treadface 100S to come into contact with the road surface toward a connectingportion thereof with the groove bottom 60 b.

As shown in FIG. 18 and FIG. 19, the side face 101 of the land block 100may have a notched part 130 that is cut out inward of the land block 100from the side face 101, and communicates with at least one side of thelug groove 60.

FIG. 18 is an enlarged perspective view of a tread section 5 inaccordance with another embodiment. FIG. 19 is a plan view of acircumferential land portion 70A in accordance with another embodimentin the tread face view.

The notched part 130 is formed in the buttress section 9 that is theside face of the land block 100, which crosses in the tread widthdirection twd. The notched part 130 is formed outer from a lineconnecting the groove bottoms 60 b of the lug grooves 60 in front of andbehind the land block 100 in the tire circumferential direction tcd toeach other in the tire radial direction trd.

The notched part 130 is formed at one end of the side face 101 of theland block 100 in the tire circumferential direction tcd. The notchedpart 130 is notched inward from the side face 101 of the land block 100(in the tread width direction twd), and communicates with the lug groove60 in the tire circumferential direction tcd. The side face 101 of theblock 100 and the lateral groove face 103 have an opening 131.

A length Lk of the notched part 130 in the tire circumferentialdirection is smaller than a length WB of the land block 100 in the tirecircumferential direction tcd.

The depth ds of the notched part 130 from the side face 101 of the landblock 100 in the tread width direction twd is constant along the tirecircumferential direction tcd of the land block 100. The opening 131 ofthe notched part 130, which is formed in the side face 101 of the landblock 100, is rectangular when viewed in the tread width direction twd.The notched part 130 is formed in the surface of the tread section 5 inparallel.

As shown in FIG. 19, when the tire 1 rotates in the rotation directiontr1, an air flow (relative wind) AR generated by the rotation of thetire 1 flows into the notched part 130, and flows along the notched part130 in the direction opposite to the rotation direction tr1. The airflow AR flowing along the notched part 130 hits against the lateralgroove face 104 of the land block 100 located behind in the rotationdirection tr1, and is guided to the lug grooves 60. As a result, airaround the tire 1 is taken into the lug grooves 60 to increase the flowrate of air flowing in the lug grooves 60. This can improve the thermalconductivity of the lug grooves 60, lowering the temperature of thetread section 5.

A depth ds of the notched part 130 may become larger as the notched part130 gets closer to the lug groove 60 with which the notched part 130communicates.

As shown in FIG. 20 and FIG. 21, the side face 101 of the land block 100may have a protruding part 150 protruding in the tread width directiontwd.

FIG. 20 is an enlarged perspective view illustrating a tread section 5in accordance with another embodiment. FIG. 21 is a plan viewillustrating a circumferential land portion 70A in accordance withanother embodiment in the tread face view.

The protruding part 150 is formed near the lug groove 60 located on oneside of the side face 101 of the land block 100 in the tirecircumferential direction tcd. The other side of the side face 101 ofthe land block 100 in the tire circumferential direction tcd issubstantially smooth. Substantially smooth described herein allowsminute irregularities due to manufacturing deviation. The minuteirregularities are, for example, irregularities within 10% of the lengthof the land block 100 in the tread width direction twd.

A length Lr of the protruding part 150 in the tire circumferentialdirection tcd is smaller than the length WB of the land block 100 formedin the circumferential land portion 70A in the tire circumferentialdirection tcd.

The protruding part 150 is a rectangle linearly extending in the tireradial direction trd, and the tire radial direction trd may be inclinedto the longitudinal direction of the rectangle. In this case, an anglethat the center line of the protruding part 150, which is set at thecenter portion in the tire circumferential direction tcd, forms with thetire normal line (that is, tire radial direction trd) may be |γ|≦60°.The protruding part 150 shown in FIG. 20 and FIG. 21 is arranged suchthat the tire radial direction trd matches the longitudinal direction ofthe rectangle and the tread width direction twd matches the lateraldirection of the rectangle.

The multiple protruding parts 150 may be formed on the side face 101 ofthe land block 100. The multiple protruding parts 150 may be linearlyarranged along the tire radial direction trd.

The multiple protruding parts 150 may be inclined to the tire radialdirection trd when viewed in the tread width direction twd.

The protruding parts 150 are not necessarily rectangular. The crosssection of the protruding part 150, which is perpendicular to thelongitudinal direction, may be triangular. The cross section of theprotruding part 150, which is perpendicular to the longitudinaldirection, may be shaped like a trapezoid having a bottom attached tothe side face 101 of the land block 100 as a long side. The crosssection of the protruding part 150, which is perpendicular to thelongitudinal direction, may be shaped like a trapezoid having a bottomattached to the side face 101 of the land block 100 as a short side. Thecross section of the protruding part 150, which is perpendicular to thelongitudinal direction, may be inclined toward one side in the rotationdirection. The protruding part 150 may be a parallelogram when viewed inthe direction along the tire rotary axis. The protruding part 150 may beformed such that a width of the central portion in the longitudinaldirection is smaller than a width at an end in the longitudinaldirection when viewed in the direction along the tire rotary axis. Theprotruding part 150 may be elliptical when viewed in the direction alongthe tire rotary axis. Other shapes that can disturb air passing thesurface of the tire are available.

In the above-mentioned embodiment, both land blocks 100 in the treadwidth direction twd have the respective air supply mechanisms andhowever, the present invention is not limited to this. Only one landblock 100 in the tread width direction twd may have the air supplymechanism. The different land blocks 100 may have air supply mechanismsof different shapes.

(7.2) Projection Parts

In the above-mentioned embodiment, the projection parts 500 are flatplate-shaped and however, may take other shapes. The projection parts500 may have a wave form shape in the tread face view, or may have ashape that is thick near the groove center line WL and becomes thinnertoward the side wall 50B1 and the side wall 50B3 (or vice versa), forexample.

Although the projection parts 500 are provided away from both the sidewall 50B1 and the side wall 50B3, the projection parts 500 are notlimited to this case. The projection parts 500 may be provided away fromonly one side wall (the side wall 501 or the side wall 50B3). Forexample, the ends of the projection parts 500 located on forward sidesin the rotation direction tr1 (the upper sides of the projection parts500 in FIG. 7) may be provided away from the side wall (side wall 501).

Each of the projection parts 500 may be provided away from the side wall50B1 and the side wall 50B3 and also be separated into segments as inthe foregoing modification example.

The number of projection segments into which each projection part 500 isseparated is not limited to two, but may be any number of two or more.

FIGS. 22(a) to 22(g) are views illustrating modification examples of thesectional shape of the projection part 500. As shown in FIGS. 22(a) to22(g), in the sectional shape of the projection part 500 (as shown inFIG. 9), the upper end is not necessarily flat. In the sectional shapeof the projection part 500, the upper end may be inclined or arcuate.

The angle θf, the groove depth D, and the groove width W may fail tosatisfy the conditions determined in the above-mentioned embodiment.

The projection parts 500 are provided on only the circumferential groove50B and however, may be provided on other places. The projection parts500 may be formed in the circumferential groove 50C formed in an areaincluding the tire center line CL, or may be provided on thecircumferential groove 50C.

(7.3) Others

Although the circumferential groove 50B extends parallel to the tirecircumferential direction tcd in the above-mentioned embodiment, thepresent invention is not limited to this. The circumferential groove 50Bis not necessarily parallel to the tire circumferential direction tcd.For example, the circumferential groove 50B may not be parallel to thetire circumferential direction tcd as long as an angle that thecircumferential groove 50B forms with the tire center line CL is 45degrees or less. The circumferential groove 50B is not necessarilylinear, and may be curved outward in the tread width direction twd ortake a zigzag pattern. Preferably, the circumferential groove 50B takesthe zigzag pattern so as not to lower the rate of air flowing throughthe circumferential groove 50B.

In the above-mentioned embodiment, the circumferential groove 50B isformed such that the length DL from the belt end 30 e to the groovecenter line WL in the tread width direction twd is 200 mm or less andhowever, the present invention is not limited to this. Thecircumferential groove 50B may be formed such that the length DL islarger than 200 mm.

The lug grooves 60 may extend to the circumferential groove 50C, and thegroove bottoms of the circumferential grooves 50 may have the projectionparts 500. That is, the circumferential grooves provided with theprojection parts 500 may be formed in an area including the tire centerline CL. This can decrease the temperature of the tread section 5.

All the lug grooves 60 are formed at the same angle to the tirecircumferential direction tcd, but may be formed at different angles. Inone tire, the inclined angles φ of the lug grooves 60 are notnecessarily the same. The inclined angle φ of the lug groove 60 may varybetween the lug groove 60 located near one end in the tread widthdirection twd and the lug groove 60 located near the other end in thetread width direction twd. In addition, the inclined angles φ may varyamong the lug grooves 60 located near one end in the tread widthdirection twd. The inclined angle φ of the lug groove 60 may be lessthan 15 degrees. The inclined angle φ of the lug groove 60 may be morethan 60 degrees.

The tire 1 according to this embodiment is extremely suitable forso-called extra-large tires, but may be applied to general tires.

The tire according to the present invention may be a pneumatic tire or asolid tire filled with rubber. Alternatively, the tire may be a tirefilled with a gas other than air with a rare gas such as Argon, anitrogen or the like.

As described above, the present invention includes various embodimentsthat are not described herein. Therefore, the technical scope of thepresent invention is determined based on only subject matters in CLAIMSthat properly derived from the above description.

Note that the entire content of Japanese Patent Application No.2012-150915 (filed on Jul. 4, 2012) are incorporated herein byreference.

INDUSTRIAL APPLICABILITY

As described above, the tire according the present invention caneffectively suppress a temperature rise of the tread section duringdriving of the vehicle, which is advantageous especially in theheavy-loading tire and the aircraft tire.

The invention claimed is:
 1. A tire comprising: a tread section providedwith a groove portion formed to extend in a tire circumferentialdirection; and a plurality of projection parts provided on a groovebottom of the groove portion, wherein each of the projection partsextends from one of side walls forming the groove portion toward theother side wall opposed to the one side wall, the projection parts arearranged at predetermined intervals in the groove portion, arelationship of 0.75 L≦P≦10 L is satisfied in a tread face view of thetire, where L denotes a length of the projection parts along a groovecenter line passing a widthwise center of the groove portion, and Pdenotes the predetermined intervals, a relationship of 0.4≦FW/W<1 issatisfied, where W denotes a groove width of the groove portion and FWdenotes a length of the projection parts in an orthogonal directionwhich is orthogonal to the extending direction of the groove portion,wherein each of projection parts is separated into plural projectionsegments in a tread face view and is provided with an opening which isformed in a center of the projection part in an extending direction ofthe projection part, and an angle θf is 10 degrees to 60 degrees, bothinclusive, where θf denotes an angle that the extending direction of theprojection parts and the groove center line form in a direction oppositeto a rotation direction of the tire in a tread face view of the tire. 2.The tire according to claim 1, wherein a relationship of 0.03 D<Hf≦0.6 Dis satisfied, where Hf denotes a height of the projection parts from thegroove bottom, and D denotes a depth of the groove portion from a treadface to the groove bottom.
 3. The tire according to claim 1, wherein arelationship of DC/OD≧0.015 is satisfied, where OD denotes a tire outerdiameter, and DC denotes a rubber gauge of the tread section at aposition on a tire center line.
 4. The tire according to claim 1,wherein a relationship of 1.25 L<P≦10 L is satisfied.
 5. The tireaccording to claim 1, further comprising: a buttress section extendinginward in a tire radial direction from a tread end that is an outer endof the tread section in a tread width direction, and extendingcontinuous to a side wall section that forms a side face of the tire; alateral groove portion extending from the groove portion to the buttresssection, and having an opening in the buttress section; and acircumferential land portion opposed to the lateral groove portion withthe groove portion interposed by the circumferential land portion andthe lateral groove portion, wherein a recess portion is formed on thecircumferential land portion and located in an extending direction ofthe lateral groove portion, the recess portion is triangular in thetread face view, a length of the recess portion in a tread widthdirection gradually increases from one point of connecting pointsbetween the groove portion and the recess portion toward a vertex of therecess portion, and gradually decreases from the vertex of the recessportion toward the other point of the connecting points between thegroove portion and the recess portion, the vertex of the recess portionis located on a position which is located in the extending direction ofthe lateral groove portion, the vertex of the recess portion isdisplaced from a center line of the lateral groove portion, and thecenter line of the lateral groove portion passes through middle pointsof the lateral groove portion, which are located at a center of thelateral groove portion in a direction orthogonal to the extendingdirection of the lateral groove portion.
 6. The tire according to claim1, further comprising: a buttress section extending inward in a tireradial direction from a tread end that is an outer end of the treadsection in a tread width direction, and extending continuous to a sidewall section that forms a side face of the tire; a lateral grooveportion extending from the groove portion to the buttress section, andhaving an opening in the buttress section; and a plurality of landportions defined by the lateral groove portion and the groove portion,wherein each of the land portions comprise a tread face to come intocontact with a road surface; the side face located outward of the landportion in the tread width direction, a first lateral groove facedefining a side wall of the lateral groove portion on one side of theland portion in a tire circumferential direction, and a second lateralgroove face defining a side wall of the lateral groove portion on theother side of the land portion in a tire circumferential direction, theland portion is provided with an air supply mechanism for air supply tothe lateral groove portion, the air supply mechanism is a tapered facecrossing the tread face, the side face, and the first lateral grooveface, at a corner position formed by the tread face, the side face, andthe first lateral groove face, two land portions opposed to each otherwith the lateral groove portion interposed are disposed such that thefirst lateral groove face of one land portion is opposed to the secondlateral groove face of the other land portion, and the second lateralgroove face is not provided with the tapered face.
 7. The tire accordingto claim 1, further comprising: a buttress section extending inward in atire radial direction from a tread end that is an outer end of the treadsection in a tread width direction, and extending continuous to a sidewall section that forms a side face of the tire; a lateral grooveportion extending from the groove portion to the buttress section, andhaving an opening in the buttress section, wherein the lateral grooveportion extends to be inclined to the tread width direction, the lateralgroove portion extends to be inclined to the tread width direction, andan inclined angle of the lateral groove portion to the tread widthdirection is 15 degrees to 60 degrees, both inclusive.